title: Prevalence of first-step mutants among levofloxacin-susceptible isolates of Streptococcus pneumoniae in north Lebanon.
abstract: Resistance of Streptococcus pneumoniae to fluoroquinolones arises by stepwise accumulation of spontaneous point mutations in the quinolone-resistance determining regions (QRDRs). Fluoroquinolones treatment of infections caused by first-step mutants (pre-resistant) can lead to the selection of resistant isolates, resulting in treatment failure. First-step mutants cannot however be reliably detected by routine resistance testing. Levofloxacin has been used as a surrogate marker to predict fluoroquinolone susceptibility in clinical laboratories. By use of a PCR followed by pyrosequencing, we examined 45 levofloxacin-susceptible pneumococcal strains [minimal inhibitory concentration (MIC) < 0.5 μg/ml] for first-step parC and parE mutations in the QRDR: 51.2% of isolates were recovered from pulmonary and nasal secretions, 22.2% from blood, 24.4% from ear and eye discharge, and 2.2% from cerebrospinal fluid. The results showed that three strains (6.6%) had first-step parC (Asp83-Asn) or parE (Asp435-Asn) mutations. This test could be useful for some high-risk patients or in national surveys.
authors.forename: Fouad
authors.initials: F
authors.lastname: Dabboussi
authors.forename: Saria
authors.initials: S
authors.lastname: Allouche
authors.forename: Hassan
authors.initials: H
authors.lastname: Mallat
authors.forename: Monzer
authors.initials: M
authors.lastname: Hamze
mesh_terms: D001769:Blood / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D004423:Ear / Q000382:microbiology; D005123:Eye / Q000382:microbiology; D024841:Fluoroquinolones / Q000494:pharmacology; D006801:Humans; D007861:Lebanon / Q000453:epidemiology; D064704:Levofloxacin / Q000494:pharmacology*; D008168:Lung / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009666:Nose / Q000382:microbiology; D011008:Pneumococcal Infections / Q000453:epidemiology*; D015995:Prevalence; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification*
chemical_list: D024841:Fluoroquinolones; D064704:Levofloxacin
keywords: Fluoroquinolones,; Lebanon,; Levofloxacin,; QRDR,; Streptococcus pneumoniae; parC,; parE,